My 1500 sierra developed a knock under my feet whenever I hit a bump.

What is your question?

Now the gear shift pin has disappeared , the rpm gauge stays in one place, weird messages appear such as door open when they are closed. Seat belt light flashes when my belt is on and i am the only one in the veh. I can still shift gears including reverse but forward gears I do not know what gear I am driving in or how fast I am going!!

What makes this problem better or worse?

veh is parked cannot use it

How long has your 2011 GMC Sierra 1500 had this problem?

Just now